This morning, David Letterman made a rare guest appearance on Regis & Kelly and didn't go easy on Jay Leno, busting out an impersonation and pointing out that Jay's claim he and Conan O'Brien got screwed over is ridiculous.

Then while explaining how he got Jay and Oprah Winfrey to appear in their Super Bowl commercial, he revealed that he originally asked Conan, Sarah Palin, and George W. Bush to appear in the spot before Oprah, but Palin couldn't do it because she was "checking her traps," and Bush "got his necktie caught in a margarita blender."

In the next segment, Letterman made fun of his own recent scandal, and said friends have helped him through it. Regis wants to be friends with Letterman too, and begged Dave to hang out with him in real life and let him be an uncle to his son Harry. Letterman and Kelly Ripa explained that this will never happen because Regis is desperate and creepy.